It has always been an object for the speaker industry to design speakers having enhanced audible sound performance. However, due to some practical limitations, such as size of the speaker and material of the enclosure of the speaker, the achievement of desired sound performance can be very difficult, particularly for speakers having relatively small size.
For a conventional speaker, typically in the form of closed box, the whole enclosure of the speaker should be theoretically designed as rigid as possible. It is normally understood that any vibration of the speaker enclosure will do harm to the sound quality of the speaker system. FIG. 1 shows a diagram of a typical closed box design of a conventional speaker 10, which comprises a transducer 12 that converts the input electric energy to the out sound energy and an enclosure 14.
However, with the conventional structure, only “half” of the sound produced by the speaker system can be heard by people. That is, the sound inside the enclosure generated by the transducer of the speaker system with the phase opposite to the audible sound outside the enclosure may vanish in the enclosure and not be audible to the listener. Indeed, the sound output by the speaker is not favorable particularly in the bass performance. The poor bass performance is further exaggerated in a minimized speaker due to its inherent disadvantage in producing bass sound.
There are some speaker designs that have been proposed to tackle this problem. FIGS. 2 and 3 show a design having a passive radiator and a vented box design, respectively. In fact, the general concepts of both designs are similar, that is, to provide the speaker system with an additional member to redirect the vanished sound energy to produce audible sounds. Normally, a passive radiator looks like a speaker without the magnet and electronic structure attached to it. The major components of a passive radiator are a cone, a suspension, and a frame. The passive radiator is basically a reactionary device as the name suggests. When a driver, such as a subwoofer, is mounted to a sealed speaker enclosure, the physical forward/back movement of the speaker affects the internal air pressure of the enclosure. When a passive radiator is mounted to the same speaker box, the internal air pressure fluctuations caused by the movement of the driving speaker causes the passive radiator to begin to move forward/back as if it was also a driving speaker. When the passive radiator moves, it creates sound frequencies just as a normal driver does. As can be seen in FIG. 2, a passive radiator 22 is provided on the enclosure 24 of the speaker system 20, and creates sound frequencies as a result of the movement thereof caused by the internal air pressure fluctuations, which is caused by the movement of the transducer 26 (the driving speaker) of the speaker system 20. Therefore, the design with a passive radiator 22 makes use of some sound energy inside the enclosure 24, which may otherwise be vanished in a conventional closed box structure, and produces more audible sounds therefrom. Similarly, the vented box design shown in FIG. 3 provides a “bass-reflex” port tube 32 in the speaker system 30 for redirecting the sound energy which may otherwise be vanished and output more audible sounds (mainly the low frequency-bass).
In both designs, the sound energy inside the enclosure of the speaker may be utilized to some extent. With a carefully designed passive radiator 22 or bass-reflex port tube 32, the speaker system 20 or 30 can produce improved sound (mainly bass), as compared with the conventional closed box design. However, as stated above, since it is normally understood that any vibration of the speaker enclosure will do harm to the sound quality of the speaker system, none of the designs in the prior art has tried to make use of the vibration of the speaker enclosure to further improve the sound performance of the speaker system. On the contrary, designers of speaker system almost always try to eliminate the vibration of the speaker enclosure as much as possible.
However, the inventor's study has shown that the vibration of the enclosure of the speaker system can be used to produce even further improved sound performance for a speaker system. Thus, the present invention aims to provide a new speaker that improves the sound performance by utilizing the vibration of the enclosure of the speaker.